4-pyrimidinethione compounds as fog inhibitors

ABSTRACT

4-Pyrimidinethione compounds are prepared by reaction of acyl isothiocyanate-tertiary enamine adducts with primary amines or ammonia. They are useful photographic fog inhibitors.

United States Patent Inventor Robert W. Lamon Rochester, N.Y.

Appl. No. 751,745

Filed Aug. 12, 1968 Patented Oct. 26,1971

Assignee Eastman Kodak Company Rochester, N.Y.

4-PYRIMIDINETHIONE COMPOUNDS AS FOG INHIBITORS 19 Claims, No Drawings U.S. Cl 96/109, 260/251 Int. Cl G03c 1/34, C07d 5/18 Field of Search 96/ 109;

Primary Examiner-Norman G. Torchin Assistant Exam iner-Richard E. Fichter Attorneys-W. H. .I. Kline and William E. Neely ABSTRACT: 4-Pyrimidinethione compounds are prepared by reaction of acyl isothiocyanate-tertiary enamine adducts with primary amines or ammonia. They are useful photographic fog inhibitors.

4-PYRIMIDINETHIONE COMPOUNDS AS FOG INHIBITORS The present invention relates to a process for preparing certain 4-pyrimidinethione compounds and to their use as fog inhibitors in photography.

During development of a silver halide emulsion, small amounts of silver halide are reduced to metallic silver regardless of whether or not they have been exposed. This reduction of silver ion produces a background fog which is more specifically referred to as chemical fog.

Chemical fog, apparent in most silver halide systems, has been reduced by prior art methods of processing exposed silver halide material in the presence of compounds which restrict development of unexposed silver halide. Such compounds can be incorporated in the silver halide emulsion or in the processing solutions for developing such silver halide emulsions. Compounds which have been found to have a chemical fog inhibiting effect on emulsions which have been subjected to high temperature and high humidity conditions are referred to as emulsion stabilizers. On the other hand, compounds which have been found to have chemical fog inhibiting effects on emulsions which have not been exposed to adverse storage conditions are referred to as antifoggants. Although a large number of emulsion stabilizers and antifoggants have been used in the prior art, many of these compounds cause undesirable losses in emulsion speed and contrast and others lack adequate compatibility with emulsion gelatin.

it has now been found that fog reduction can be achieved by incorporating a small amount of certain 4-pyrimidinethiones in light-sensitive silver halide emulsions. The present invention includes a process for the production of certain 4- pyrimidinethiones, light-sensitive silver halide emulsions containing a 4-pyrimidinethione compound described hereinafter as an antifoggant and a photographic element comprising a support having coated thereon a light-sensitive silver halide emulsion layer containing a 4-pyrimidinethione compound described hereinafter as an antifoggant.

The 4-pyrimidinethione compounds utilized as antifoggants in accordance with the present invention have the formula:

wherein R represents hydrogen or the organic portion ofa primary organic amine, R represents an alkyl group, an aralkyl group, e.g., benzyl or phenethyl, or a benzene nucleus, R represents hydrogen, lower alkyl, lower alkoxy, carb(lower alkoxy) or a benzene nucleus, R represents hydrogen or lower alkyl, and wherein R and R collectively represent a polymethylene chain having at least two carbon atoms, such as ethylene (-CH cH trimethylene -cn cn cn tetramethylene (-CI-l2 3 23l-l CH2-) pentamethylen e (CH CH CH CH CH or hexamethylene (-Cl-hCl-hCl-h CH CH CH,-), for example. When R is a benzene nucleus, it is norm ally phenyl.

The term lower alkyl" when used herein and in the claims, unless specifically indicated otherwise, refers to an alkyl group having one to six carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl or hexyl, for example.

The term lower alkoxy when used herein and in the claims, unless specifically indicated otherwise, refers to an alkoxy group having one to six carbon atoms such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, pentyloxy or hexyloxy, for example.

The term a benzene nucleus" when used herein and in the claims, unless specifically indicated otherwise, refers to phenyl and substituted phenyl nuclei such as alkylphenyl, alkoxyphenyl, halophenyl or hydroxyphenyl nuclei, for example. Illustrative alkylphenyl nuclei include, for example, (o-,m-,p-)- methylphenyl, (o-,m-,p-)ethylphenyl, (o-,m-,p-)propylphenyl, (o-,m-,p-)isopropylphenyl or (o-,m-,p-)butylphenyl. (o-,m-,p- )-methoxyphenyl, (o-,m-,p-)ethoxyphenyl, (o-m-,p-)propoxyphenyl, (o-,m-,p-)isopropoxyphenyl or (o-,m-,p-)butoxyphenyl, for example, are illustrative alkoxyphenyl nuclei. (0- ,m-,p-)-chlorophenyl, (o-,m-,p-)fluorophenyl or (o-,m-,p- )bromophenyl, for example, are illustrative halophenyl nuclei. (o-,m-,p-)-hydroxyphenyl are illustrative of hydroxyphenyl nuclei.

Methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, pentyloxycarbonyl or hexyloxycarbonyl, for example, are illustrative of carb( lower alkoxy) groups,

The 4-pyrimidinethione compounds having the formula I are prepared in accordance with the process of the invention by reacting an acyl isothiocyanate-tertiary enamine adduct having the formula:

II are R;\\ /C--NERI i 11 \NR.

wherein R, R and Rl have the meaning previously assigned to them and R,,and R,,each represents an alkyl group such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, octyl, decyl, etc., for example, especially a lower alkyl group having one to six carbon atoms and a benzene nucleus, and wherein collectively represents a saturated 5 or 6 membered heterocyclic nucleus such as l-pyrrolidinyl, piperidino, morpholino. l-pyrazolidinyl or 3-oxazolidinyl, for example, with an amine having the formula RNH wherein R has the meaning previously assigned to it.

The adducts having the formula II are prepared by reacting a tertiary enamine having the formula:

III

wherein R,, R,,,R and R have the meaning previouslyassigned to them with an acyl isothiocyanate having the formula:

wherein R, has the meaning previously assigned to it.

Illustrative of the amines having the formula RNl-l are, for

example, ammonia, alkylamines such as, for example,

methylamine, ethylamine, propylamine, isopropylamine, bu-

tylamine, isobutylamine, pentylamine, hexylamine, heptylamine, octylamine, decylamine, dodecylamine, etc., hydroxyalkylamines such as, for example, 2-hydroxyethylamine, 3-hydroxypropylamine, 3-hydroxybutylamine, 4- hydroxybutylamine, S-hydroxypentylamine, -hydroxyhexylamine, etc.; alkoxyalkylamines, such as, for example, 2-

methoxyethylamine, 2-ethoxyethylamine, 2-propoxyethylamine, 2-butoxyethylamine, 3-methoxypropylamine, 3- ethoxypropylamine, 3-propoxypropylamine, 4-methoxybutylamine, 4-ethoxybutylamine, etc., aralkylamines such as benzylamine or phenethylamine, for example, a carboxyalkylamine, such as, for example, carboxymethylamine, 2-carboxyethylamine, 3-carboxypropylamine, 4-carboxybutylamine, Scarboxypentylamine, G-carboxyhexylamine, etc., an H N-(CH ),,-COOalkyl amine, wherein n represents a whole number from 1 to 4, such as, for example,

(HgNCHjCHgN 4-(aminopropyl)morpholine, 4-(aminobutyl)morpholine, l- (Z-aminoethyl)pyrrolidine, l-(2-aminoethyl)-2-methyl-pyrrolidine or l-(2aminoethyl)piperidine, for example.

As just noted, the adducts having the formula ll are prepared by reacting a tertiary enamine having the formula III with an acyl isothiocyanate having the formula IV. The reaction is preferably carried out at room temperature, but the temperature may vary from about l C. to about 35 C. Advantageously, the reaction is carried out in an inert solvent in which the adducts are insoluble, such as, for example, dimethyl ether, diethyl ether, diisopropyl ether, p-dioxane, dimethoxyethane, benzene, etc., or chlorinated solvents, such as, for example, chloroform, dichloroethane, tetrachloroethane or carbon tetrachloride. A particular method of preparing tertiary enamine adducts is described by S. Hunig, K. Hubner and E. Benzig, in Chem. Ber. 95, 937-9 l962).

The 4-pyrimidinethione compounds having the formula I are prepared by reacting an adduct having the formula II with an amine having the formula RNH wherein R has the meaning previouslyassigned to it. The reaction is normally carried out with agitation, such as stirring, in the presence of an inert solvent under basic reaction conditions. Suitable inert solvents include water and a lower alkanol such as, for example, ethanol, n-propyl alcohol or isopropyl alcohol. The reaction takes place without the necessity of heating and is preferably carried out at ambient conditions of temperature (i.e., about 10 C. to about 35 C.) and pressure, but an elevated temperature (e.g., above ambient temperature to about 100 C.) may be used to hasten the reaction. The basicity of the reaction mixture is advantageously maintained at a level, for example,

as, for

sufficient to preclude precipitation of intermediate reaction products before the reaction has an opportunity to proceed to the desired 4-pyrimidinethione product. In most cases the use of an excess of the amine compound having the formula provides a sufficiently basic medium to solubilize intermediate reaction products through which reaction to the 4- pyrimidinethione product may proceed. In the event precipitation of any intermediate reaction product occurs, such intermediate product can be removed from the reaction mixture or can easily be converted to the 4-pyrimidinethione product by heating in the presence of a strong base, as is shown in the examples given hereinafter.

The preparation of the adducts having the formula ll and .the 4-pyrimidinethione compounds having the formula I is illustrated hereinafter. Temperatures in the examples and elsewhere herein are in degrees Centigrade unless otherwise indicated.

Example I To a solution of 13.7 g. (0.10 mole) of l-(N-pyrrolidino)cyclopentene in 70 ml. of dry diethyl ether was added dropwise, with cooling and stirring, 10.! g. (0.10 mole) of acetyl isothiocyanate in 10 ml. of dry diethyl ether. After stirring in the cold for 2 hours, the orange precipitate which formed was collected, washed thoroughly with dry diethyl ether, then with ml. of cold methanol, and finally with more dry diethyl ether. The resulting air-dried l-(N- acetylthiocarbamoyl)-2-( N-pyrrolidino)-cyclopentene melted at l49-l50 C. dec. and weighed 20.0 g. Recrystallization from ethyl acetate to which was added a little methanol gave the analytical sample as orange prisms, m.p. l54-l55C. dec. The infrared spectrum (KBr) showed maxima at 3.15;. (NH) and 5.95 (C=0). The N.M.R. spectrum agreed with the assigned structure in all respects.

The enamine product thus produced and identified as l-(N- acetylthiocarbamoyl)-2-(N-pyrrolidino)-cyclopentene, 6.00 g. (0.025 mole), was suspended in 70 ml. of concentrated aqueous ammonia and the mixture was stirred until a solution formed. Ethanol (30 ml.) was added portionwise to hasten solution. After standing overnight the solution was concentrated under vacuum and acidified to yield 3.72 g. of a tan colored solid, mp 234-236 C. dec. Recrystallization from methanol gave pale yellow needles of 6,7-dihydro-2-methyl-5 H-cyclopentapyrimidine-4(3H)-thione having an unchanged melting point.

Example 2 B-diethylaminostyrene was reacted with benzoyl isothiocyanate in accordance with the method described in example v1 for the preparation of the enamine adduct except that the reaction mixture was not cooled. During the course of the addition of the benzoyl isothiocyanate, a-(N-benzoylthiocarbamoyl)-B-diethylaminostyrene separated as a red oil which, as the mixture was stirred for several hours at room temperature, gradually solidified and granulated. The product was purifled by precipitating from chloroform solution with ligroin (b.p. 35-60). Two repetitions of this process gave the analytical sample as red-orange prisms, m.p. l3l-l32 C. dec. The infrared and N.M.R. spectra were consistent with the assigned structure.

The tertiary enamine adduct obtained as just described when reacted in equimolar amounts with cyclohexylamine and aqueous ethanol in a manner similar to that described in example l resulted in the precipitation of an intermediate product having the structure:

v 4 When uiiii'eafiimcfihtnifiiaTe B'r'oiii was added to a 0.5N solution of sodium hydroxide in 50 percent aqueous ethanol and heated on a steam bath it cyclized to form 1- cyclohexyl-2,5-dipheny1-4( lH)-pyrimidinethione having the TABLE II formula: I 2,5-diphenyl-4(1H)-pyrimidinethiones VI S S 11 II 5 o H oiHi-o 1 5 N H-C C-C6H5 J-C5Hs N N Yield Recrystalliza- S Example percent M.P., C. tion solvent which, after recrystallization from ethanol melted at 215217 10 OHECHZOH 60 3221-223 32mg? 11 CH; 55 214-216 Chloroformethanol. Example 3 12 casein. =63 225-227 Acetonitrile. To a stirred suspension of 2.00 g. (0.0073 mole) of the v enamine adduct of example 1 in ml. of ethanol was added 2 i Yield based on crude material, ml. of 2-aminoethanol. The resulting mixture was stirred for 2 2 52 yield hours during which time its color changed from orange to WL 20 Certain enamine adducts obtained from the reaction of terlow. 6,7-Dihydro-l-(Z-hydroxyethyl)-2-methyl-5H-cyclopentiary enamines and acyl isothiocyanates are unstable and yield tapynmidme4 lH)-thlone preclpnated as 3 50nd was colon heatin in ethanol 21 4-oxazinethione An exam le of such lected, washed with ethanol and then air dried. Yield, 1.27 g.,

o o an enamine adduct 15 that resulting from the reaction of l-(N- m.p. 240 -243 C. dec. Two recrystallizations from dimethylmm holino): clohe tene and benzo l isothioc anate In formamide gave the analytical sample as yellow plates, m.p. 25 p y p y these cases the corresponding 4-pyrimidinethlone compound 243-245C. dec. 4

Th can be obtained from the 4-oxazinethione compound as fee of amlme were added to a suspenslon of described hereinafter The 4- yrimidinethione com ounds in- (0.0l26 mole) of 1(N-benzoylthiocarbamoyl)-2-(N- P p volved are those wherein R and R collectively represent morpholino)cyclopentene in 35 ml. of ethanol. The resulting tetrameth km or emameth lene mixture was warmed briefly on a steam bath and stirred at 30 y p 16 i room temperature for 30 minutes, or until allthe red starting 6 7 9 y 3 drox y hen I material was r placed by a yellow-orange solid Product. The 5H cycloheptapyrim$1164:1H) thio:e y solid product was collected, washed with ethanol and air isothiocyanate 16 3 g (010 mole) was added dropwise dried IAIfi]inoz'(N'PenmylthmcarbamPyl)cyclopemani with stirring, to an ice cold solution of 18.1 g. (0.10 mole) 1- was thus obtained, weighing 3.77 and having a m.p. of 164 (N-morpholino)cycloheptene in dry ether. The mixture was C. (transition). Two recrystallizations from chloroformkept cold for Several hours and he orange Solid which ethanol gave t anflyt'cal sample as fine yellow'orange precipitated was collected by suction filtration. After washing dleS*m'P'168 l70 thoroughly with ether, the solid, which became sticky on Four gralns (Q0214 mole) of the Product llust bt amed was 40 standing, was dissolved in 500 ml. of ethanol and the resulting Suspended m a of sod'um hydroxlde solution filtered hot. Concentration ofthe filtrate to about 150 cent aqueous ethanol. The mixture was heated and swirled for and cooling gave tha 4 oxazinethione intermediate 10 minutes on a Steam bath for 1 hour at room productas orange needles. Yield l 1.4 g. of6,7,8,9-tetrahydroe a u fi-P P "Y "-Y P P- 2-phenyl-5H-cyclohepta-1,3--oxazine-4-thione, m.p. 170- py m Preclpnaled a yellow solld 5 172 C. Two recrystallizations from ethanol gave the analytiproduct, was collected, washed well with ethanol and air calsample as brmiamorange needlesmp dried. Yield, 2.99 g., m.p. 230.-235 C. dec. Two recrystal- CHCI: lizations from ethanol gave the analytical sample as yellow max :292 rodsi P- (e 2100), 341(e 13500). The infrared spectrum shows no NH Employing the general P e ur of example 4 addmonal or c 0 bonds. The N.M.R. spectrum is consistent with J- y Y P PY 0 were 6,7,8,9-tetrahydro-2-phenyl-5 H-cyclohepta-l ,3-oxazine-4- prepared and are summarizedin the following Table l. thione.

TABLE I Four grams (0.0155 mole) of the oxazine intermediate 6,7-dihydro-5H-cyclopentapyrimidine--thlones roduct obtained as 'ust described was refluxed in a solution P 1 s of 25 ml. of ethanol and 4 ml. of Z-aminoethanol until all the l orange starting material was replaced by a bright yellow solid N product (about 2 hours). Yield 4.04 g. of 6,7,8,9-tetrahydro- I l-(2-hydroxyethyl)-2-phenyl-5H-cycloheptapyrimidine-4 L (1H)-thione, m.p. 226-227 C. dec. Recrystallization from N chloroform-ethanol gave tiny yellow needles of unchanged it melting point.

Yield Recrystalliza- Example R R1 percent M.P., 0. Lion solvent 5 H C5H5 79 195-197 Methanol. 6 CH3 05115 76 240-244 Acetonitriln. 7 CHQCHZOI'I 05H; 227-220 Ethanol.

8 CHzCHzN O 05H; 40 200-201. Ethanol.

S1 CH OH; 77 202-203 Ethyl acetate.

I Yield based on crude material. b Dec.

Additional 2,5-diphenyl-4(1H)-pyrirriidinethiones listed in Table 11 hereinafter were prepared using the general procedure ofexample 2.

Employing the general procedure of example 13 additional 6,7,8,9-tetrahydro-2-phenyl-5H-cycloheptapyrimidine- JCOHl5 Yield percent Recrystalliza- Example R M.P.,C. tionsolvent 263-265 chloroformethanol. 20F209 Ethanol.

(DH-CH3 18 CHzCHzN I) 212-213 Ethanol. 178-180 Methanol.

49 169-171 Ethanol.

; grade material, based on 4-oxazinethione intermedite.

The conversion of 6,7,8,9-tetrahydro-2-phenyl-5-cycloheptoxazine-4-thione to 6,7,8,9-tetrahydro-2-phenyl-5H- cyclopeptapyrimidine-4-thione compounds by refluxing with a primary amine in a solution of ethanol has been disclosed in examples l3 -l8.

However, it has been found that if 6,7,8,9-tetrahydro-2- phenyl-SH-cycloheptoxazine-4-thione is treated at room ternperature with the primary organic amines, especially the more reactive primary organic amines, for example, alkylamines, the same products are obtained in improved yield. The use of hindered primary amines, such as isopropylamine or neopentylamine, for example, gives intermediate products which can be converted to the desired 4-pyrimidinethione products by treatment with an alkali. Preferably the alkali is employed in dilute form, such as, for example, 0.5 N alkali in 50 percent aqueous ethanol. When an alkali is needed the use of an appropriate dilute alkali will be readily apparent to one skilled in the art to which this invention is directed. The reaction scheme is illustrated hereinafter.

1 s s II II I lio...

Unhlndered amine Room temperature dilute alkali Hlndered OH amine Room temperature (2) s 8 ll II 1 H5 Room temperature I H 0 i dilute (4) alkah J-CQIIS N I A mixture of aniline and (I) did not react appreciably although the mixture was maintained at room temperature for 24 hours. Reaction does occur when a mixture of aniline and (l) is refluxed together; 6,7,8,9-tetrahydro-l,2-diphenyl-5H- cycloheptapyrimidine-4( lH )-thione was so obtained.

Example 19 Preparation of 6,7,8,9-Tetrahydro-2-phenyll -propyl-5H- cycloheptapyrimidine-4-( l H )-thione A mixture of 2.57 g. (0.0l mole) of 6,7,8,9-tetrahydro-2- phenyl-SH-cycloheptoxazine-4-thione having the formula l hereinbefore and 2 ml. of propylamine in 25 ml. of ethanol was stirred, without heating, for l.25 hr. The yellow product was isolated by filtration, washed with fresh solvent and airdried. Yield, 2.81 g., m.p. 212 dec. Recrystallization from ethanol gave pure product, m.p. 2 l2-2 l 3dec.

Example 20 Preparation of l-Hydroxy-2-(N-neopentylbenzimidoylthiocarbamoyl)-cycloheptene A mixture of 2.57 g. (0.01 mole) of 6.7.8.9-tetrahydro-2- phenyl-5H-cycloheptoxazine-4-thione having the formula I hereinbefore and 2.6 ml. of neopentylamine in 20 ml. of ethanol was stirred, without heating, for L25 hours. The suspension which formed was filtered to give 2.14 g. of the adduct, l-hydroxy-2-(N-neopentylbenzimidoylthiocarbamoyU- cycloheptene which after solution in dichloromethane and dilution with ligroin was recovered as a solid, m.p., l55-l 56 dec.

Example 2l Preparation of 6,7,8 ,9-Tetrahydro-l-neopentyl-Z-phenyl-SH- cycloheptapyrimidine-4( lH)-thione One gram (0.00290 mole) of l-hydroxy-2-(N-neopentylbenzimidoylthiocarbamoyl)-cycloheptene prepared as described in example 20, was warmed and swirled with 10 ml. of 0.5 N NaOH in50 percent ethanol. The suspension which formed was stirred at room temperature for 1 hour, chilled, and filtered. After washing with aqueous ethanol the product weighed 0.88 g. (yield 93 percent), m.p. 2l8-2 19 after softening and darkening at 209-2l0 Recrystallization from acetonitrile gave pure product melting at 22 l 222 C. dec.

The identical material was also obtained by refluxing a mixture of 2.57 g. (0.01 mole) of 6,7,8,9-tetrahydro-2-phenyl-5H- cycloheptoxazine-4-thione and 2.6 ml. of neopentylamine in 20 ml. of ethanol for 4.5 hr. (56percent yield).

The corresponding 4-pyrimidinethione compound wherein R and R collectively represent tetramethylene, i.e., 5,6,7,8-

tetrahydro-l-neopentyl-2-phe11y lquinazoline-4(1H)thione was similarly obtained by refluxing a mixture of 2.31 g. (0.0l mole) of 5,6,7,8-tetrahydro-2-phenylbenzoxamine-4(1H)- and 2.6 ml. of neopentylamine in 20 ml. of ethanol for 3 hr. A yield of 95 percent was obtained. Upon recrystallization from acetonitrlle the purified product melts at 2l6-217.5 C.

thione Table IV hereinafter sets'forth data with respect to various i 5 intermediates used in preparing the 4pyrimidinethione antifoggant compounds. N Table V hereinafter sets forth data with respect to 6,7- JCUHS dihydro-5H-cyclopentapyrimidine-4-thione compounds. It

0 10 supplementsTablel.

TABLE IV Calculated Found Molecular Intermediate Yield (m.p.C.) Recrystallization solvent formula C H N S C H N S 84% Ethyl acetatemethan0l CuHxaN-gOS 60.5 7.6 11.8 13.5 60.6 7.6 12.0 13.3 CSNHCOCHz (Example l) C5H C=CHN(C:H5)2 52% (131-132) Chlorolormllgroln CzaHzzNzOS 71.0 6.6 8.3 9.5 70.8 6.7 8.2 0.3 csNgcocom (Example 2) I 92% (168-170 den.) Chlorofonnethanol ..C1oH1aN2OS 70.8 5.6 8.7 9.9 70.5 5.8 8.6 9.8 [p s NHC 00.115 NHCoHt 85% (16546666 3.) .(10 Oral-12 N 05 72.5 6.5 7.7 8.8 72.4 6.7 7.5 8.8 C5H C=CHNH- iSNHCOCBHI (Exa p e 6,7;8,9- tetrahydro-2-phenyl-5H- 44% (171-173 dec.) Ethanol C H NOS 700 5.9 5.4 12.4 69.9 5.5 5.3 12.4

eyeloheptoxazlne-4-thlone.

Yields based on crude material.

TABLE V Calculated Found Yield, Molecular percent formula C H N S C II N S Amaxn E-lO- Example 1 s0 cameos 57.0 0.1 10.0 10.3 57.0 0.1 16.8 10.4{ 3-3 3 72 Owl-114N108 57.1 6.7 13.3 15.2 57.3 6.6 13.6 15.0 "343 25.2 4 74 CwHmNzS 75.0 5.0 0.2 10.5 74.0 5.0 a.010.7{ 243 19.4 5 79 CHHHNQS 68.4 5.3 12.3 14.1 68.4 5.4 12.1 14.0{ 303 12.4 50 5.5 6 76 C H NZS 69.4 5.8 11.6 13.2 60.2 5.8 11.4 13.4 348 10.0 7 s0 C|5H15N20S 50.2 5.0 10.3 11.8 50.0 5.0 10.5 1-. .0{ s 40 01.11.311.05 66.8 6.8123 0.4 00.7 0.0 12.0 0.1{ 0 77 CvHnNaS 00.0 0.7 15.0 17.8 00.0 0.0 15.0 10.0{

Yield based on crude matcnal.

Overall yield. Determined in ethanol unless otherwise indicated.

d Detennined in chloroform.

Determined in dimethylfornxamidc.

Table VI hereinafter sets forth data with respect to 2,5- in i compounds h n in T ble IX wi h dilute diphenyl-4( lH )-pyrimidinethione compounds. NaOH.

TABLE VI Calculated Found Yteld, Molecular percent formula C H N S C N 11 S M11911. E--

Example:

2 69 CzzHzzNzS 76.3 6.4 8.1 9.3 76.0 6.5 8.1 9.2 354 19.8 60 CtaHreNzOS 70.1 5.2 9.1 10.4 59.9 5.5 9.1 1o.a{ gig 55 C17H14N2S 73.4 5.1 10.9 11.5 73.4 5.0 9.9 11.5 351 16.9 =63 CzaHtaNzS 77.9 5.2 7.9 9.0 77.7 5.2 7.8 8.9 354 18.3

* Yield based on crude material. b Overall yield. v Determined in chloroform, except for second compound which was determined in ethanol.

Table Vll hereinafter sets forth data with respectto 6.7.8.9- While dilute NaOl-l was the alkali actually employed tetrahydro-Z-phenyl-5l-l-cycloheptapyrimidine-4( lH)-thione wherein treatment with a dilute alkali is involved herein it will C mP H be understood that the other alkalies such as potassium TABLE v11 Calculated Found Yleld,= Molecular percent formula C H N S C H N S hmax. c E-lO- 86 C17H20N2OS 68.0 6.1 9.3 10.7 67.8 7.0 0.1 10.0 363 18.0 41 CZtHzoNzS 75.9 6.1 8.4 9.7 75.8 6.0 8.2 0.8 M52 23.0 19 01.11.251.51 72.5 7.4 9.4 10.7 72.3 7.5 9.2 10.5{ g 16 s5 ClQHZZNHS 72.5 7.4 9.4 10.7 72.3 7.5 9.2 10.5{ 3:3 243 16.3 253 15.9 17 96 CH10N7S 70.3 6.3 10.9- 12.5 70.5 6.5 10.8 12.7 308 127 365 6.0 245 9.5 18 CzrHzrNgOS 68.3 7.4 11.4 8.7 68.0 7.6 11.7 8.7{ "348 177 Crude material, based on -oxazlnethione intermediate. b Determined in chloroform. a Determined in ethanol.

Table Vlll hereinafter lists various 4( lH)-pyrimidinethione 40 hydroxide and lithium hydroxide. for example, can be compounds prepared in accordance with the present invensimilarly employed. tion. These compounds were prepared by reacting the appropriate primary organic amine with the oxazine compound Other compounds that can be prepared in accordance with corresponding to the desired 4( ll-l)-pyrimidinethione. In the the invention include 5,6,7,8-tetrahydro-l.Z-diphenylquincase of the unhindered amines the reactions were carried out azoline-4( lHj-thione, 6,7-dihydro-l-n-butyl-2-methyl-5H- at room temperature. Refluxing was employed in the case of cyclopentapyrimidine-4-thione, 6,7-dihydro-l-n-butyl-2- hindered amines. phenyl-5H-cyclopentapyrmidine-4-thi0ne. 1-ethyl-2.5-

Table lX hereinafter sets forth data with respect to various diphenyl-4( lH)-pyrimidinethione, l-n-butyl-2.5 -diphenyl- 4 intermediate compounds which can be cyclized. as shown (IT-D-pyrimidinethionE. l--hydroxypropyl-2,5-diphenylhereinbefore, by treatment with dilute alkali, for example, to 0 4( lH)-pyrimidinethione. 6,7,8,9-tetrahydro-l-methyl-2- obtain 4( l H)-pyrimidinethione compounds containing a phenyl-SH-cycloheptapyrimidinc-4( lH-thione, 6.7.8.9- phenyl group attached to the carbon atom in the 2-position. t tr h d o-1-n-buty|-2-phenyl-5H-cycloheptapyrimidine-4( 1 Table X hereinafter sets forth data with respect to the H )-thione, 5.6.7.8-tetrahydro-l-methyl-2-phenylquinazoline- 4( 1H) compounds containing a phenyl group attached to the 4( lH)-thione and 5,6,7,8tetrahydro-l-n-butyI-2-phenylquincarbon atom in the 2-position prepared by cyclization of the azoline-4( lH-thione, for example.

LII

TABLE VIII Recrystal- Calcd. Found Yield, lization CHCh R 15 percent M.P.,C. solvent Formula C H N S C H N S Amax. EXlO- CH2CH2CHa.-..- 5 94 212-213 dec. Ethauol..... CmHszNzS 72.5 7.4 9.4 10.7 72.3 7.6 9.2 10.5 243 9.4

245 9. CHzCHzN 6 5 76 -172 ..(10 C2|H27N3OS 68.3 7.4 11.4 8.7 68.0 7.6 11.7 8.7{

94 226227 dec. Chloroform- CwHmNgOS 68.0

ethanol CH2CH2OH.-.... 6

78 $9450 dec. Acetonltt'llo C19H2|N2S 73.0 7.

Methanol CnHnNzS 71.8 87 198-200 Acetonitrile. C1aH22NzS 72.4

TABLE IX.INTERMEDIATES CSNHC|7=NR H) 08111 Recrystal- Calculated Found Yield, lizatlon CHCIJ, R 11 percent M.P.. C. solvent', Formula C H N S C H N S Am. EXw-a cmctonoanh 5 62 155-156de0. C20H25N20S 69.7 8.2 8.1 9.3 60.4 8.1 8.0 9.5{ 28? 65 161-162(160. 33?: 0211111118208 10.8 1.0 1.9 0010.6 7.6 1.6 8.0{ 28; 298 10.2 H 4 88 165-166dec,. d0 C19H29N20s 6 -1 4m 3 o 161-162. 5 281 12. 2 4 00 deg" .-..do .CH11N10S 10.1 1.1 8.2 9.4 10.1 8.0 1.8 9.1{ 401 15'? 011101101 a .65 138-140(180- 01.111.11.08 i Crude.

TABLE x 4(1H)-pyrlmldlmethlon0 compounds Recrystal- Calculated Found Yield, llzatlon CHCI; R 11 percent M.P.,C. solvent Formula C H N S C H N 8 max. 11x10- cmmcm): 5 93 221-222 Acetonltrlle 02011211828 18.6 8.0 8.6 0.8 18.8 8.3 8.4 0.1{ {3 5 02 241-2420. Ethanol..." 021111118108 74.6 1.1 8.3 9.5 74.6 1.8 8.3 9.4

Cmcwrm. 4 96 218-2116 8861011111110- 01111210118 73.0 1.1 0.0 10.3 12.1 1.8 8.8 10.4{ l 4 81 235-236(160. Ethanol.. CzoHznNzS 14.0 1.8 8.6 0.0 14.0 7.3 8.6 0.8

The advantage of using mild reaction conditions is illustrated by the following chart:

The term hindered amine" as used herein refers, for example, to a primary organic amine which is branched at the 1- position and reacts with difficulty. lsopropylamine, secondary butylamine, tertiary butylamine and cyclohexylamine, disclosed herein, are hindered amines of the character just defined. Neopentylamine is also a hindered amine. Broadly the term hindered amine as used herein covers primary amines which undergo reaction with difficulty because of steric hindrance. Steric hindrance is believed to be the reason why amines, otherwise suitable (sufficiently basic, etc.) react with difficulty. Aniline, for example, is not a hindered amine as this term is used herein.

The effectiveness of the 4-pyrimidinethiones in reducing fog according to the invention is shown in the following examples summarized in Table IV. ln the examples, samples of the compounds listed were added to separate portions of a high-speed silver bromoiodide emulsion which has been panchromatically sensitized with a cyanine dye. Each emulsion sample was coated on a cellulose acetate film support at a coverage of 459 mg. ofsilver and 1040 mg. of gelatin per square foot. A sample of each film coating was exposed on an Eastman 1B sensitometer, processed for 5 minutes in H Kodak Dl (;50 developer, fixed, washed and dried. The results reported are in relation to control.

TABLE IV One week Fresh test incubation test Cone. g./ Rela- Rela- Compound of mole of tive tive Example N0. silver speed 7 Fog speed 7 Fog Control 100v 1.53 .16 54 1.09 .49 5 .09 85 1.38 .17 68 1.18 .22 71 1.23 .20 59 1.00 .22 59 1.18 .16 33 1.08 .24 95 1.38 .15 83 1.25 .18 82 1.45 .16 45 1.22 .37 69 1.35 .19 40 1.20 .43

Control 100 1.43 .15 63 1.13 .38 .0009 91 1.25 .14 08 1.15 .33 16 .0009 100 1.37 .14 71 1.18 .32 17 .0009 97 1.33 .13 65 1.10 .32

The preparation of photographic silver halide emulsions such as are suitably stabilized with the 4-pyrimidinethiones of the invention typically involves three separate operations:

1. emulsification and digestion of silver halide,

2. the freeing of the emulsion of excess water-soluble salts, suitably by washing with water, and

3. the second digestion or after-ripening to obtain in-- creased emulsion speed or sensitivity. (Mees, The Theory of the Photographic Process," 1954). The new antifoggants can be added to the emulsion before the final digestion or afterripening or it can be added immediately prior to the coating.

The silver halide emulsion or photographic element containing the antifoggants of this invention can contain conventional addenda such as gelatin plasticizers, coating aids, and hardeners such as aldehyde hardeners, e.g., formaldehyde, mucochloric acid, glutaraldehyde bis(sodium bisulfite), maleic dialdehyde, aziridines, dioxane derivatives and oxypolysaccharides. Spectral sensitizers which can be used are the cyanines, merocyanines, complex (trinuclear) cyanines, complex (trinuclear) merocyanines, styryls, and hemicyanines. Sensitizing dyes useful in sensitizing such emulsions are described. for example, in U.S. Pat. Nos. 2,526,632 Brooker and White, issued Oct. 24, 1950, and 2,503,776 of Sprague, issued Apr. 1 1, 1950. Developing agents can also be incorporated into the silver halide emulsion if desired or can be contained in a contiguous layer. Various silver salts can be used as the sensitive salt such as silver bromide, silver iodide, silver chloride, or mixed silver halides such as silver chlorobromide or silver bromoidide. The silver halides used can be those which form latent images predominantly on the surface of the silver halide grains or those which form latent images inside the silver halide crystals such as described in U.S. Pat. No. 2,592,250 of Davey and Knott issued Apr. 8, 1952.

The silver halide emulsion layer of a photographic element containing the antifoggants of the invention can contain any of the hydrophilic, water-permeable binding materials suitable for this purpose. Suitable materials include gelatin, colloidal albumin, polyvinyl compounds, cellulose derivatives, acrylamide polymers, etc. Mixtures of these binding agents can also be used. The binding agents for the emulsion layer of the photographic element can also contain dispersed polymerized vinyl compounds. Such compounds are disclosed, for example, in U.S. Pat. Nos. 3,142,568 of Nottorf, issued July 28,

1964; 3,193,386 of White, issued July 6, 1965; 3,062,674 of Houck, Smith and Yudelson, issued Nov. 6. 1962; and

3,220,844 of Houck, Smith and Yudelson, issued Nov. 30, 1965; and include the water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

The silver halide emulsion of a photographic element containing the antifoggants of the invention can be coated on a wide variety of supports. Typical supports are cellulose nitrate film, cellulose ester film, polyvinyl acetal film, polystyrene film, poly(ethylene terephthalate) film and related films or resinous materials as well as glass, paper, metal and the like. Supports such as paper which are coated with a-olefin polymers, particularly polymers of a-olefms containing two or more carbon atoms, as exemplified by polyethylene, polypropylene, ethylene-butene copolymers and the like can also be employed.

The speed of the photographic emulsions containing the antifoggants of the invention can be further enhanced by including in the emulsions a variety of hydrophilic colloids such as carboxymethyl protein of the type described in U.S. Pat. No. 3,011,890 of Gates, .Ir., Miller and Koller, issued Dec. 5, 1961, and polysaccharides of the type described in Canadian Pat. No. 635,206 of Koller and Russell issued Jan. 23, 1962.

Photographic emulsions containing the antifoggants of the invention can also contain speed-increasing compounds such as quaternary ammonium compounds, polyethylene glycol or thioethers. Frequently, useful effects can be obtained by adding the aforementioned speed-increasing compounds to the photographic developer solutions instead of, or in addition to, the photographic emulsions.

Photographic elements containing the antifoggants of the instant invention can be used in various kinds of photographic systems. In addition to being useful in X-ray and other nonoptically sensitized systems, they can also be used in orthochro-' matic, panchromatic and infrared sensitive systems. The sensitizing addenda can be added to photographic systems before or after any sensitizing dyes which are used.

Silver halide emulsions containing the antifoggants of the invention can be used in color photography, for example, emulsions containing color-forming couplers or emulsions to be developed by solutions containing couplers or other colorgenerating materials, emulsions of the mixed-packet type such as described in U.S. Pat. No. 2,698,794 of Godowsky, issued Jan. 4, 1955; in silver dye-bleach systems; and emulsions of the mixed-grain type such as described in U.S. Pat. No. 2,592,243 of Carroll and Hanson, issued Apr. 8, 1952.

Silver halide emulsions containing the antifoggants of the invention can be sensitized using any of the well-known techniques in emulsion making, for example, by digesting with naturally active gelatin or various sulfur, selenium, tellurium compounds and/or gold compounds. The emulsions can also be sensitized with salts of noble metals of Group VIII of the Periodic Table which have an atomic weight greater than 100.

Silver halide emulsions containing the antifoggants of the invention can be used in diffusion transfer processes which utilize the undeveloped silver halide in nonimage areas of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a silver layer in close proximity to the original silver halide emulsion layer. Such processes are described in U.S. Pat. Nos. 2,352,014 of Rott, issued June 20, 1944; 2,543,181 of Land, issued Feb. 27, 1951; and 3,020,155 of Yackel, Yutzy, Foster and Rasch, issued Feb. 6, 1962. The emulsions can also be used in diffusion transfer color processes which utilize a diffusion transfer of an imagewise distribution of developer, coupler, or dye, from a light-sensitive layer to a second layer, while the two layers are in close proximity to one another. Silver halide emulsions containing the antifoggants of the invention can be processed in stabilization processes such as the ones described in U.S. Pat. No. 2,614,927 of Broughton and Woodward, issued Oct. 21, 1952,and as described in the article Stabilization Processing of Films and Papers by H. D. Russell E. C. Yackel and J. S. Bruce in P.S.A. Journal, Photographic Science and Technique, Volume 168, Oct. 1950.

The antifogging agents of this invention can be incorporated to advantage during manufacture in silver halide emulsions representing the variations described above. Moreover, fog control in binderless silver halide films prepared by vapor deposition of silver halide on a suitable support can be achieved by coating the antifogging agents of the invention over the vapor deposited layer of silver halide. 7V

Combinations of all the above-mentioned addenda can be used if desired.

The amount of antifoggant can vary quite widely and, in general, will be less than 1 g. per mole of silver. A greater amount can be effectively used where the antifoggant is incorporated in a layer other than the silver halide emulsion layer, and a lesser amount, generally less than 0.5 g. per mole of silver, and preferably less than 0.1 g. per mole of silver, can be used in the silver halide emulsion layer. The minimum amount is not critical since no adverse effect is incurred by using small amounts. However, it is preferred to use at least 0.0001 g. per mole of silver to obtain a suitable level of fog reduction.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinbefore and as defined in the appended claims.

lclaim:

l. A light-sensitive photographic silver halide emulsion containing silver halide and a compound selected from the 4- pyrimidinethione compounds having the formula:

wherein R represents hydrogen, an alkyl group having one to 12 carbon atoms, a hydroxyalkyl group having two to six carbon atoms, an alkoxyalkyl group having three to eight carbon atoms, a carboxyalkyl group having two to seven carbon atoms, a (CH,),,-COO(alkyl having one to four carbon atoms) group, a (CH ),,-N(alkyl having one to four carbon atoms) group, an aralkyl group, phenyl, tolyl, ethylphenyl, alkoxyphenyl, chlorophenyl, bromophenyl, hydroxyphenyl, xylyl, 4-biphenylyl, 4-(alkyl having one to four carbon atoms)morpholino, l-ethylpyrrolidinyl, l-ethyl-2-methylpyrrolidinyl, l-ethylpiperidino, n represents an integer of from I to 4, R, represents an alkyl group, an aralkyl group or a benzene nucleus, R represents hydrogen, lower alkyl, lower alkoxy, carb(lower alkoxy) or a benzene nucleus, R represents hydrogen or lower alkyl, wherein R and R collectively, may represent a polymethylene chain having at least two carbon atoms as an antifoggant, and wherein the amount of antifoggant present ranges from at least 0.0001 gram to about 1 gram per mole of silver present in the silver halide emulsion.

2. A light-sensitive photographic silver halide emulsion in accordance with claim 1 wherein R and R collectively, may represent trimethylene, tetramethylene or pentamethylene.

3. A light-sensitive photographic silver halide emulsion in accordance with claim I wherein R, is phenyl and wherein R and R collectively, may represent trimethylene, tetramethylene or pentamethylene.

4. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and a compound selected from the 4-pyrimidinethione compounds having the formula:

wherein R (including 11) is defined as in claim 1 as an antifoggant, and wherein the amount of antifoggant present ranges from at least 0.0001 gram to about l gram per mole of silver present in the silver halide emulsion.

5. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and a compound selected from the 4-pyrimidinethione compounds having the formula:

S II

wherein R (including n) is defined as in claim 1, R, represents a lower alkyl group, an aralkyl group or a benzene nucleus as an antifoggant, and wherein the amount of antifoggant present ranges from at least 0.0001 gram to about 1 gram per mole of silver present in the silver halide emulsion.

6. A light-sensitive photographic silver halide emulsion in accordance with claim 5 wherein R, is phenyl.

7. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and a compound selected from the 4-pyrimidinethione compounds having the formula:

wherein R (including :1) is defined as in claim I as an antifoggant, and wherein the amount of antifoggant present ranges from at least 0.0001 gram to about 1 gram per mole of silver present in the silver halide emulsion.

8. A light-sensitive photographic silver halide emulsion in accordance with claim 7 wherein R represents a lower alkyl group.

9. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and a compound selected from the 4-pyrimidinethione compounds having the formula:

wherein R (including n)'is defined as in claim 1 as an antifoggant, and wherein the amount of antifoggant present ranges from at least 0.0001 gram to about 1 gram per mole of silver present in the silver halide emulsion.

10. A light-sensitive photographic silver halide emulsion in accordance with claim 9 wherein R represents a lower alkyl group.

11. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and 6,7- dihydro-Z-methyl-SH-cyclopentapyrimidine-4( 3H )-thione as an antifoggant.

12. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and 6,7- dihydro-2-phenyl-5H-cyclopentapyrimidine-4( l H )-thione as an antifoggant.

1 20 13. A light-sensitive photographic silver halide emulsion in thereon a layer containing a light-sensitive emulsion of claim accordance with claim 1 containing silver halide and 6,7- dihydro-l-methyl-2-phenyl-5H-cyclopentapyrimidinethione 17. A photographic element comprising a support having 4( ll-l)-thione as an antifoggant. v thereon a layercontaining a light-sensitive emulsion of claim 14. A light-sensitive photographic silver halide emulsion in 5 accordance with claim 1 containing silver halide and 2,5- A P g p element comprisin! PP havin! diPheny]-1-(2 hyd|-oxyc;hy|)-4(|H)-pyrimidin[hione as an thereon a layer containing a light-sensitive emulsion of claim antifoggant. 5

15. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and 2,5- diphenyll -methyl-4( lH )-pyrimidinethione as an antifoggant.

16. A photographic element comprising a support having 19. A photographic element comprising a support having thereon a layer containing a light-sensitive emulsion of claim 33? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,615,621 Dated October 26, i 971 Inventor(s) Robert W I lOn It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

C "I H S ol 2, 1 11'18 3?, N 3 hould be R3 I Col. 1 line 62, "(-CH CH CH CH2C Should be -(-CH CH CH CH CH )E.. f

Col. 5', line 27, delete "14.".

Col. 5, between lines 2? and 28, insert ---Exemple L centered.

Col. 6, line 32, "6, 7,9, 9" should read --6, 7,8, 9--- Col. 6, line 3h, insert --Benzoyl-- before "isothiooyanate" Col. 6, line Q9, 21 0o) should be 21 ooo)---.

Col. 8, line M6, after "cyoloheptene" insert having the formula--.

Col 9, line 3, phenylbenzoxemine" should be heny1- benzoxazine- Table IV, first structure should be CSNHCOCH UNITED STATES PATENT OFFICE E9) CERTIFICATE OF CORRECTION Patent No. 3,615,621 Dated October 26. I 9Y1 Inventofls) Robert I'! It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

.. Page 2 Table V, last line under heading "Found C", "60.6" should be 6OIO I Table VI, line 5, 69" should be e9--- Table VII, line 5, underhe ading "Calculated H", "6.1

should be ---6. 7.

Col. I 'I line 51;, after "L (iH) insert ---pyrimidinethione-- Col 1 2, line 51 "L HH-thione" should be -Ll('|H)-thione--- Table VIII, StI'IOGUIe should be Table VIII, heading "EX1 0'" should be ---E X 1 o- Table X, heading "EXIO'B should be ---E X 1O' UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,615,621 Dated October 26, 1 971 Inventor(s) Robert Lamon It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[- Page 3 Table X, structure should be (CE )W Col. 13, first structure on left should be H II Col 1 9, line 3, "cyclopentapyrimidinethione" should be ---cyolopentapyrimidine--.

Signed and sealed this 5th day of December- 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK testing Officer Commissioner of Patents 

2. A light-sensitive photographic silver halide emulsion in accordance with claim 1 wherein R2 and R3, collectively, may represent trimethylene, tetramethylene or pentamethylene.
 3. A light-sensitive photographic silver halide emulsion in accordance with claim 1 wherein R1 is phenyl and wherein R2 and R3, collectively, may represent trimethylene, tetramethylene or pentamethylene.
 4. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and a compound selected from the 4-pyrimidinethione compounds having the formula:
 5. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and a compound selected from the 4-pyrimidinethione compounds having the formula:
 6. A light-sensitive photographic silver halide emulsion in accordance with claim 5 wherein R1 is phenyl.
 7. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and a compound selected from the 4-pyrimidinethione compounds having the formula:
 8. A light-sensitive photographic silver halide emulsion in accordance with claim 7 wherein R represents a lower alkyl group.
 9. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and a compound selected from the 4-pyrimidinethione compounds having the formula:
 10. A light-sensitive photograpHic silver halide emulsion in accordance with claim 9 wherein R represents a lower alkyl group.
 11. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and 6,7-dihydro-2-methyl-5H-cyclopentapyrimidine-4(3H)-thione as an antifoggant.
 12. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and 6,7-dihydro-2-phenyl-5H-cyclopentapyrimidine-4(1H)-thione as an antifoggant.
 13. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and 6,7-dihydro-1-methyl-2-phenyl-5H-cyclopentapyrimidine-4(1H)-thione as an antifoggant.
 14. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and 2,5-diphenyl-1-(2-hydroxyethyl)-4(1H)-pyrimidinethione as an antifoggant.
 15. A light-sensitive photographic silver halide emulsion in accordance with claim 1 containing silver halide and 2,5-diphenyl-1-methyl-4(1H)-pyrimidinethione as an antifoggant.
 16. A photographic element comprising a support having thereon a layer containing a light-sensitive emulsion of claim
 1. 17. A photographic element comprising a support having thereon a layer containing a light-sensitive emulsion of claim
 2. 18. A photographic element comprising a support having thereon a layer containing a light-sensitive emulsion of claim
 5. 19. A photographic element comprising a support having thereon a layer containing a light-sensitive emulsion of claim
 11. 